Participants in Massive Open Online Courses (MOOCs) come from an incredibly diverse set of backgrounds and act with a wide range of intentions (Christensen 2013, Ho 2014). Interestingly, our own recent surveys of 11 MITx courses on edX in the spring of 2014 show that teachers (versus traditional college students) are a significant fraction of MITx MOOC participants. This suggests many ways to improve and harness MOOCs, including the potential arising from the collective professional experience of participants, opportunities for facilitating educator networks, MOOCs as a venue for expert-novice interactions, and possible added value from enhancing teacher experience through accreditation models and enabling individual teacher re- use of MOOC content. Here, we present data in detail from these teacher enrollment surveys, illuminate teacher participation in discussion forums, and draw lessons for improving the utility of MOOCs for teachers.